The invention generally relates to a method and apparatus for completing a well.
When well fluid is produced from a subterranean formation, the fluid typically contains particulates, or “sand.” The production of sand from the well must be controlled in order to extend the life of the well. One way to control sand production is to install screens in the well and form a substrate around the screens to filter sand from the produced well fluid. A typical sandscreen is formed from a cylindrical mesh that is generally concentric with the borehole of the well where well fluid is produced. Gravel is packed in the annular region that surrounds the sandscreen. The produced well fluid passes through the gravel, enters the sandscreen and is communicated uphole via tubing that is connected to the sandscreen.
The gravel that surrounds the sandscreen typically is introduced into the well via a gravel packing operation. In a conventional gravel packing operation, the gravel is communicated downhole via a slurry, which is a mixture of fluid and gravel. A gravel packing system in the well directs the slurry around the sandscreen so that when the fluid in the slurry disperses, gravel remains around the sandscreen.
It is not uncommon for more than one zone to be gravel packed in a well. One way to complete a well with multiple gravel pack zones is to run a sump packer first and then one packer and screen assembly with a work string and downhole service tool. The single packer is set, and then the single zone is gravel packed. Subsequently, the service tool is retrieved to the surface. This sequence is repeated until every zone is completed with gravel pack.
Another technique to complete a well with multiple gravel pack zones is to run all of the packers and screens into the well at one time with a downhole service tool. The lower zone is completed first, and the packing proceeds uphole one zone at a time. Reverse circulation typically is used to remove sand in the service tool before it moves up to the next zone. To accomplish the reverse circulation, a tool is run inside the screens to seal off the screens above the zone being packed. However, this tool typically is quite complex, as the tool must perform the sealing and routing of the slurry and returning liquid.
For purposes of preventing sand production and ultimately completion failure, it is important to achieve effective and complete gravel placement. Without a complete pack, one or more of the screens may fail. Once a screen section has failed, the produced gravel, or sand, begins flowing into the production tubing. The sand may cause erosion, may damage flow control devices in the surface equipment and may generally shorten the life of the well.
Thus, there is a continuing need for better ways to gravel pack a multiple zone well, and there is also a continuing need for better ways to allow corrective action to be taken in the event of screen failure.